--create-metadata still ignores empty values in template

Despite of the changes in 5f89634a, --create-metadata still ignores emtpy values (I speak of the "empty presets" for the template). This is the skeleton created:

Categories:
  - repo

CurrentVersionCode: 2147483647

Funnily, not even "Name" is set (see !302 (merged) for the fix to that). Inserting a print(app) before the write gives:

{'AuthorName': '', 'Name': '', 'CurrentVersionCode': 2147483647, 'IssueTracker': '', 'Categories': ['repo'], 'Summary': '', 'SourceCode': '', 'WebSite': ''}

So the fields are there, but are not written to the yml file. Note that only happens with ruamel. When I force it to use yaml.dump(), the skeleton is created as expected – so I expect the culprit lies somewhere in metadata.write_yaml().

PS: If you want the test APK for that, it's just 10k and can be found in my repo.